That was blackmail.

However, the prestige of the Nelson name was great, the power of its money was potent, and Henry believed that he could protect himself from eventualities.

After cautious deliberation he sent word to one of his men in the Ranger field that he wished to see him.
The man came promptly, and when he left Henry Nelson's house after a conference he carried with him a perfectly clear idea why he had been sent for.

This despite the fact that he had not been told in so many words.

He knew, for instance, that a certain Calvin Gray had become a menace to his employers, so dangerous that it was worth to them a substantial fortune to be rid of him, and that while Henry Nelson could under no circumstances countenance anything illegal, anything savoring of violence, nevertheless if some accident should befall Gray, if some act of God should put an end to him, there would be no disposition on Henry's part to question the divine origin of that calamity.
Furthermore, the speaker had made it plain that if Providence did take a hand in some such mysterious manner, he would then be in a position amply to reward his employee for many acts of loyalty that had apparently passed unrecognized.